This Shared Instrumentation Grant application is for funding for the purchase of a Becton Dickinson FACSAria high-speed sorting flow cytometer. The instrument will be integrated into the Englert Cell Analysis Laboratory, which is a shared resource of the Norris Cotton Cancer Center at Dartmouth Medical School. The new flow cytometer will provide users with the up-to-date sorting and analysis capabilities that they require. The requirement for a new flow cytometer is based on several needs that are not met by the cytometers currently available at Dartmouth. The primary need is for the ability to define cells by more than four fluorescence parameters. The FACSAria will have three lasers and will permit users to excite a range of fluorochromes across the spectrum and to analyze and sort cells on any (or all) of thirteen fluorescence parameters. In addition, the FACSAria will allow users to save time and cell sample by the sorting of four populations of cells at one time; will allow cross-beam compensation to facilitate the use of overlapping fluorochromes; will facilitate the definition of cells with non-rectangular sort gates; and will provide for more efficient sorting at high cell flow rates. The Englert Cell Analysis Laboratory operates under the control of a Director, a Co-Director, and an Advisory Board, and with the technical support of a flow and imaging supervisor. Running costs are met by a subsidy from the NCI core grant to the Norris Cotton Cancer Center, by hourly charges to users, and by institutional support from Dartmouth Medical School. Additional institutional support will be provided by Dartmouth Medical School toward the purchase cost of the FACSAria. At the present time, there are 47 NIH grant holders dependent upon the flow cytometers in the Englert Core Laboratory; they hold, as PIs, 88 NIH grants. A "major user group" has been identified. These nine major users project 78% of the total use of the FACSAria cytometer. They hold, as PIs, NIH grants. [unreadable]